1. Technical Field
The present invention relates to roll state sensing including sensing of a load shift state. More particularly, the invention relates to estimation of a roll state of a vehicle, including an apparatus and method for estimating a load shift state in right and left wheels.
2. Description of the Related Art
Hitherto, methods of determining a rollover of a vehicle have been proposed. In a representative method, on a two-dimensional map using the roll angle and the roll velocity of a vehicle as parameters, a rollover region in which the roll angle and the roll velocity are relatively large and a non-rollover region in which the roll angle and the roll velocity are relatively small are set. A border line (threshold line) between the rollover region and the non-rollover region is changed according to a change direction of the steering angle of the vehicle. The state that the vehicle is at risk of rollover is determined when the history line of the actual roll angle and roll velocity of the vehicle crosses the border line (threshold line) (refer to Japanese Patent Application Laid-Open (JP-A) No. 2001-71787).
In this method, sensors are indispensable because the actual roll angle and roll velocity of a vehicle need to be detected and measured.
Consequently, an apparatus and method for estimating a load shift state of right and left wheels and an apparatus and method for estimating the roll state of a vehicle without measuring the roll angle and the roll velocity are demanded.